They are still fond of cock-fighting in the South Carolina backwoods but even the fans of this bloody sport were unprepared for the scratching and scrapping as John McCain and George Bush went at each other on the way to yesterday's primary election.

Each survives South Carolina to fight to the death another day. But as they proceed from this cockpit towards the big make-or-break states, Bush and McCain are steeling and steering their campaigns in explosively divergent directions. They now threaten to blow the Republican Party apart in a showdown between the System (Bush) and the People (McCain).

Most polls in South Carolina had showed George Bush to be the clear choice of Republican voters. Nationally, he remains a narrow favourite among Republicans. But some primaries including South Carolina are 'open', meaning that registered voters with either party (and independents) can vote across party lines, as they wish.

In South Carolina - as in other, bigger, primaries to come - McCain was overwhelming favourite with non-Republicans. Each candidate, both in South Carolina and in the nail-biting contest ahead, is fighting a different election for the same position.

Bush now fights - as he fought South Carolina - a Republican campaign for a Republican vote for the Republican nomination, the party's man and the System's man. McCain, however, is already fighting a popular presidential election against both Bush and Al Gore. Never before have local primary elections gone so rapidly national.

While Bush now turns to the party's core for survival and possible victory, McCain, both by electoral necessity and instinct, casts a net to try to catch not only Republicans but also any registered Democrats and independents (Bush calls them 'party crashers') he can entice the Republican side both now and later. Senior Democrats have even urged their own to vote for McCain in the key primaries. National across-the-board polls therefore show McCain overtaking Bush, and predict that if he can keep going, McCain - unlike Bush - could trounce Gore in the final round.

Bush is a personification of interests, opaque powers that control part - but not all - of American society: big oil, big insurance, Capitol Hill, Republican governors in statehouse mansions, and the wrath of the fundamentalist Christians. Bush must now turn and cling to these powers so long as they will back him, with no second chances.

McCain is doing just the reverse. He is growing into his own populist rhetoric, and promised on Friday to 'bring the presidency back to the People'. The so-called 'McCain swoon' became something else in South Carolina this week: harder-edged, but also more like a 'McCain hysteria'. McCain's final sweep through the old colonial and revolutionary port of Charleston on Friday was like a rock show.

McCain entered, flanked by his wife Cindy and a phalanx of local basketball stars, to a crescendo of sound. On stage, the group stood in dramatic silhouette against a vast, back-lit American flag. The music switched to the thumping of Queen's 'We Will Rock You', as the 'American Hero' was introduced. McCain has a new gesture: he punches the air with the arms everyone knows the Vietcong broke. He has taken on a pres idential sheen - people start to wonder if he might make a good, if not great, president.

Bush has also intensified his act. He unleashed a junkyard campaign of smears, often wrapped in 'push-polling' by telephone. In the televised debate with McCain he was a ruthless victor, leaving his opponent speechless on occasions. Awash with money, Bush needed a message. The press had pilloried him for fuzziness over detail, but he suddenly became the able administrator of economically-buoyant, frugally-taxed Texas, while McCain is weak on specifics.

Bush hurled the worst of insults at McCain - he is 'Clinton' - meanwhile trying to turn himself into McCain, 'a reformer with results... I never claimed to be one of the great geniuses, but I'm plenty smart. I've got good common sense, and that's what people want in a leader.'

His stuffy stump speech gave way to McCain-style 'town meetings' like that at Barnwell last week, when he fielded questions from all-comers. He called it a 'one-on-one', turned up the volume both literally and figuratively, shouting into the microphone and tapping his foot: 'What I'm ado, ' he says in best Southern, 'is remind people about my record. Remind people that I'm comin' with a record from outside Washington.'

Yet on Capitol Hill, only four out of 55 Republican senators have declared for McCain. Senators despise the upstart and there is ironic talk about how a McCain White House could work with its own party. McCain has pledged to rewrite the financial rules by which Congress was elected; he pushes for a higher tobacco tax; he breaks the rules of behaviour.

He called veteran Budget Committee chairman Peter Domenici 'an asshole' and when challenged added, 'I wouldn't call you an asshole unless you really were an asshole.' Senator Chuck Grassley is 'a fucking jerk'. Against all this, Bush - although he has never held office on the Hill - is one of the family: both the family that entwines corporate America and the Hill, and the family of his father.

On Tuesday come Arizona and Michigan, both winnable by McCain. Arizona is his home state, but ironically it is here he has enemies. Some polls show McCain the 'favourite son' to enjoy only a narrow lead.

'There is no room for complacency by either of them,' says Mike Minnaugh, chairman of the Arizona Republican Party. After Michigan the battle royal begins. On 7 March, 15 states vote on 'Super Tuesday', including two of the 'big four': California and New York. McCain can win New York, but it is of little use to him without California.

There is probably no System in the world more determined to survive than this one, and yet the more Bush tries to wield it, the more he enables McCain to reply, as he did on Friday: 'I feel like Luke Skywalker trying to get out of Death Star.'